Currently a number of waterproof breathable (WPB) films, membranes, and materials are laminated to fabrics to create a fabric for use in outerwear that is generally both waterproof and breathable. Examples of such WPB materials include polytetrafluoroethylene (PTFE) and polyethylene (PE). Because these WPB membranes are generally oleophilic they tend to attract contaminants such as oils, detergents, etc., which in turn compromises the membrane micro-pores. The effect of this contamination tends to make the membrane more hydrophilic, which dramatically lowers the waterproofness of the fabric. In one test performed, such contamination reduced the waterproofness from 21 meters water column to less than 5 meters water column.
WPB fabric manufacturers have attempted to solve this problem by applying a film of an oleophobic material to the exposed side of the WPB membrane to prevent the aforementioned pore clogging. However in certain processes, such as those processes where a polyurethane (PU) layer is used, this effectively blocks the micro-pores rendering the WPB fabric generally non breathable and hampering the performance of the fabric. Such a film is applied prior to lamination of the WPB membrane to the fabric, which due to a disparity in melting points, also impacts the ability to effectively laminate the WPB membrane to the fabric.
To avoid this problem, companies have attempted to apply different oleophobic chemicals to the exposed WPB layer using a spray deposition technique. While this tends to avoid the problem of impeding the breathability, this material is also applied during the membrane fabrication, and thus impedes the ability to adequately laminate the membrane to the fabric, and also does not provide adequate oleophobicity.
In order to further enhance the waterproof aspect of a WPB laminated fabric, a durable water repellent (DWR) treatment is often applied to the outer surface of the fabric to further improve the water repellency and thus improve the waterproof nature of the fabric. This process is performed in a separate step after the lamination of the oleophobic chemical treated WPB membrane to the fabric.
Accordingly, in any of the above-mentioned cases, a number of steps are required to manufacture a WPB fabric, which is both time and cost intensive, which ultimately makes working with WPB fabrics expensive and challenging.